Single dose dispenser units (pipetters) and multiple dose dispenser units (dispeners) are well known devices employed in the medical and scientific field. Both of these devices generally are employed for metering, or dispensing small volumes of liquid (i.e. microlitres) in a controlled manner in various testing and sampling procedures. In some procedures it is necessary to dispense single doses of various different fluids into different vials or containers. For this purpose single dose pipetters most desirably can be employed. In other applications it is necessary to inject small measured quantities of the same fluid into various different containers. For these applications multiple dose dispensers are generally employed. It has been most common for medical and scientific testing facilities to stock different devices for single and multiple dose dispensing, respectively.
In single dose dispensers (e.g. pipetters) it is most desirable to provide for easy removal of the tip, or pipette, into which the single dose of fluid to be dispensed is initially drawn. This is particulary important when various different fluids are to be sampled or tested, to thereby avoid contamination of one fluid with another. Accordingly it is highly desirable to provide an extremely simple and reliable mechanism for ejecting or removing the tip from the unit; preferably without the necessity of physically handling or touching the tip.
In multiple dose dispensers the barrel or vial in which the fluid to be dispensed is retained should be easily removable from the unit for subsequent replacement. In dispensing devices employing actuator rods extending into the barrel it is often necessary to withdraw the rod from the barrel before the barrel can be removed. When a piston head is connected to the rod it is sometimes necessary to separate the head from the rod in order to permit the rod to be withdrawn.
In both single and multiple dose dispensers it is highly desirable to provide for the adjustability of the volume of fluid to be dispensed. This should be achievable in a simple and reliable manner.
The following patents are considered to be material to the examination of this application, and are made of record herein pursuant to the requirements of 37 CFR 1.56.
Caulking guns and similar devices generally include actuating mechanisms for the multiple dose dispensing of a compound from a storage chamber or compartment. Although these devices are not at all concerned with the precision, small volume (i.e. microlitre) dispensing of fluids in the medical or scientific fields they do disclose actuating mechanisms employing an elongate rod that is relatively moveable through an opening in an actuating plate, and that is adapted to be moved in increments by the actuating plate to dispense material in multiple doses. Representative patents relating to this type of device are: U.S. Pat. Nos. 2,530,359 (Peterson); 2,602,570 (Sherbondy); 2,602,571 (Sherbondy); 2,732,102 (Ekins); 2,786,604 (Collins); 3,381,861 (Stein) and 3,997,085 (Lindquist).
In distinction to single and multiple dose dispensers employed in the medical field, the actuating mechanisms, or plates employed in the devices disclosed in the above patents are not directly engagable by the hand of the user; but rather are actuated through a trigger or other similar device to provide a mechanical advantage. Although in Peterson the lever 30 is adapted to be engaged by hand at 31, it is for the sole purpose of releasing the retaining force on the actuator rod so that the rod can be withdrawn. In other words the hand actuation of the lever 30 does not move the actuator rod to dispense a fluid from the unit. Moreover none of the above devices are designed to precisely vary the volume of a fluid to be dispensed.
Medical syringes and similar devices for varying the stroke of a dispensing plunger to vary the quantity of a fluid to be dispensed have been disclosed in the patent literature. Representative devices of this type are disclosed in U.S. Pat. Nos. 2,156,023 (McKay); 2,916,057 (Carle et al.); 3,815,790 (Allen et al.); 3,831,602 (Broadwin) and 3,831,603 (Armenti).
The McKay patent discloses a device in which adjustment of the dispensing stroke is achieved by moving concentric actuator rods 12 and 13 relative to each other. After the desired stroke has been set the concentric rods are caused to move together as a single unit by tightening the finger-operated handle 17 onto the split end of the rod 13 by tightening the bolt or stud 18. Unless and until the stud 18 is tightened the handle 17 will not be functional to dispense any fluid from the device.
In the Allen et al. device different end caps (e.g. 7) are employed to vary the length of the plunger stroke.
In the Carle et al. device a collar is moved along a plunger rod to provide an adjustable stop that limits the distance the rod can be withdrawn for taking fluid samples.
In the Broadwin device the stroke of a plunger 32 is varied by changing the effective length of a longitudinal slot 62 in a tubular support member 42. This stop functions to limit the stroke of a pusher 48 by engaging a projection 64 formed as an integral part of the pusher. Although this device employs a means for varying the stroke of the pusher rod it is not adjustable to provide both single dose and multiple dose dispensing
The Armenti patent employs measuring shelves 24 that can be adjustably mounted on its associated plunger. In this manner the position of the shelves can be varied to vary the length of plunger travel.
It is also known in the dispensing art to provide micrometer calibrations to set and indicate the volume of fluid to be dispensed from syringes, pipetters and similar dispensers. Devices of this type are represented in U.S. Pat. Nos. 2,250,467 (Cole); 2,283,915 (Cole); 3,232,117 (Gilmont); 3,334,788 (Hamilton) and 3,815,785 (Gilmont). Although these patents disclose various different arrangements of micrometer calibrations employed to set the quantity of a fluid to be dispensed; none of these patents disclose a system in which the micrometer calibrations are employed to either indicate or set the length of a dispensing slot through which a finger-engageable dispensing lever is adapted to move to provide the dispensing operation. As will be explained hereinafter, it is this latter type of arrangement that is employed in applicant's device.
It is also known in the prior art to provide syringes which can be set for either single dose or multiple dose dispensing; as represented by the disclosures in U.S. Pat. Nos. 2,457,859 (Austin) and 4,050,459 (Sanchez). Both of these devices require the formation of abutments or stops in the surface of a piston rod, and this represents a somewhat complex approach to achieving both single and multiple dose dispensing with a single unit. In fact, to the best of applicant's knowledge devices of the type disclosed in the Austin and Sanchez patents are not being commercially utilized.